Method for treating high-hardness stainless steel surface through microwave-assisted micro-forging technology

Abstract

The invention relates to a method for treating a high-hardness stainless steel surface by a microwave-assisted micro-forging technology. The method comprises the following steps: (1) soaking a workpiece in an alkaline solution to remove oil; (2) washing; (3) primary micro-forging: carrying out micro-forging by using particles with the particle size of 100-200 mu m to form roughness of 5-20 mu m; (4) immersing the workpiece subjected to primary micro-forging into an acidic cleaning solution for 30 seconds to remove dust and oxides; (5) washing the workpiece with deionized water, washing the workpiece with alcohol, and drying the workpiece in a drying oven at the temperature of 80 DEG C; (6) the workpiece is placed in a microwave cavity which is vacuumized or filled with inert gas, and then microwave radiation is carried out; (7) secondary micro-forging is conducted on the surface of the workpiece, specifically, micro-forging treatment is conducted through particles with the particle size of 20-100 microns, strengthening and morphology control are conducted on the surface of the stainless steel, and micron-sized pits are formed in the surface of the workpiece; (8) carrying out acid pickling on the workpiece subjected to secondary micro-forging treatment for 30 seconds to remove micro-particle dust; and (9) washing with deionized water, washing with alcohol, drying in a drying oven at 80 DEG C, and packaging for later use.

Description

Technical Field

[0001] The invention belongs to the technical field of metal surface strengthening, and particularly relates to a method for processing a high-hardness stainless steel surface using a microwave-assisted micro-forging technique. Background Art

[0002] Micron particle forging technology (abbreviated as: micro-forging) is a new type of metal surface strengthening and modification technology developed on the basis of traditional shot peening technology. This technology uses a high-speed (above 200m / s) microparticle (particle size of 20-200μm) flow to forge and strike the metal surface, instantly changing the surface coarse crystals into fine crystals, on the one hand, improving the density of the metal surface structure, on the other hand, forming an ordered metal fiber organization, and finally obtaining deformation strengthening of the organizational structure within the range of 20-40μm surface depth, resulting in the processed metal workpieces being significantly improved in plasticity, toughness, finish, corrosion resistance and fatigue strength, and has been well applied to multiple metal material products such as harmonic gears and springs. The deeper the depth of the microparticle flow on the metal surface, the better the strengthening effect. As far as the current micro-forging process technology is concerned, the above-mentioned strengthening effect can be obtained for conventional metal alloy workpieces, but when processing the surface of high-hardness alloy materials, the depth area of ​​its strengthening effect is greatly limited, resulting in the strengthening effect failing to meet the expected requirements.

[0003] Microwaves are a type of electromagnetic waves with a frequency between 300MHz and 300GHz. Microwave heating methods have the characteristics of non-contact heating, selective heating, rapid heating and volumetric heating. For bulk smooth metals, microwaves interact with them only on the metal surface and cannot perform volumetric heating, which manifests as reflected electromagnetic waves. At the same time, as a good conductor, metals have an obvious skin effect under electromagnetic fields. The alternating electromagnetic field induces a surface electric field on the metal surface, and the generated induced current is only distributed on its surface, causing Joule heating. The higher the microwave frequency, the stronger the metal's conductivity, the more obvious the skin effect, and the smaller the skin depth. Summary of the invention

[0004] The purpose of the present invention is to overcome the deficiencies in the above-mentioned prior art and provide a method of cooperating between primary micro-forging roughening, microwave irradiation and secondary micro-forging to achieve a substantial improvement in material hardness and fatigue life, strengthen the stainless steel surface and control the morphology, generate micron-level pits on the workpiece surface to improve the hardness of the stainless steel workpiece, optimize the fatigue resistance of the parts, and use the characteristic of skin heating of metal conductors by microwaves to solve the pain points of microparticle forging of high-hardness alloys, increase the depth of strengthening effect of microparticles on high-hardness materials, and greatly extend the service life of high-hardness alloy material workpieces. A method for treating the surface of high-hardness stainless steel with microwave-assisted micro-forging technology. Another purpose of the present invention is to provide a method for treating the surface of high-hardness stainless steel with microwave-assisted micro-forging technology, which only strengthens the metal surface while the inside of the metal is not affected, and after the metal surface temperature rises and the surface metal becomes soft and tough, the strengthening area and effect after microparticle forging are increased, while the original properties of the metal inside remain unchanged.

[0005] The technical solution of the present invention is the method for treating the surface of high-hardness stainless steel with the microwave-assisted micro-forging technology, which is special in that it includes the following steps:

[0006] ⑴ Soak the workpiece in alkaline solution to remove oil;

[0007] ⑵ Wash with water;

[0008] ⑶First-level micro-forging: Micro-forging with particles with a particle size of 100-200 μm to form a roughness of 5-20 μm;

[0009] (4) Immerse the workpiece after primary micro-forging in an acid cleaning solution for 30 seconds to remove dust and oxides;

[0010] ⑸ Rinse the workpiece with deionized water, alcohol, and dry it in an oven at 80°C;

[0011] (6) Place the workpiece in a microwave cavity that is evacuated or filled with inert gas, and then irradiate it with microwaves;

[0012] ⑺ Perform secondary micro-forging on the workpiece surface: Use particles with a particle size of 20 to 100 μm for micro-forging to strengthen the stainless steel surface and control the morphology, and generate micron-sized pits on the workpiece surface;

[0013] ⑻ Pickle the workpiece after the secondary micro-forging treatment for 30 seconds to remove the fine dust particles;

[0014] ⑼ Rinse with deionized water, rinse with alcohol, dry in an oven at 80℃, and package for later use.

[0015] Preferably, the alkaline degreasing in step (1) refers to immersing the workpiece in an alkaline degreasing solution for 5 to 10 minutes at 50 to 90° C. to remove oil stains and fingerprints on the surface of the workpiece.

[0016] Preferably, the washing in step (2) refers to rinsing with deionized water for 10 to 30 seconds.

[0017] Preferably, the first-level micro-forging in step (3) is to micro-forge the workpiece surface with 120-160 μm white corundum particles to form a roughness of 5-20 μm on the workpiece surface to increase the surface's absorption of microwaves.

[0018] Preferably, the acid cleaning solution in step (4) is composed of the following components by weight: 5 parts of sulfuric acid, 5 parts of hydrochloric acid, and 90 parts of water, and is used to remove oxide scale, metal powder generated by primary micro-forging, and residual particles embedded in the surface of the workpiece.

[0019] Preferably, the drying in step (5) refers to baking the workpiece in an oven at 80-120° C. for 2-5 minutes.

[0020] Preferably, the microwave frequency in step (6) is 2.45 GHz, the radiation time is 30 to 60 s, and the radiation power is 1000 to 3000 W.

[0021] Preferably, the secondary micro-forging in step (7) means that the particle size is between 20 and 100 μm, the coverage is 100%, the micro-forging scanning speed is 20 to 5 mm / s, the particle shooting speed is 200 to 350 m / s, and the angle between the spray gun and the workpiece surface is 15 to 90°.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] (1) The present invention strengthens and controls the morphology of the stainless steel surface through a method combining microwave radiation heating and secondary micro-forging, generates micron-sized pits on the workpiece surface, improves the hardness of the stainless steel workpiece, and optimizes the fatigue performance of the parts.

[0024] (2) The present invention utilizes the characteristic of skin heating of metal conductors by microwaves to achieve heating of the metal surface only without causing any heat treatment effect on the inside of the metal. In this way, the surface temperature of the metal rises, the surface metal becomes softer and tougher, and the strengthening area and effect of the microparticles after forging are increased, while the original properties of the metal inside remain unchanged. In short, only the surface is strengthened while the inside is not affected.

[0025] ⑶ The experimental results of the present invention show that only the cooperation of primary micro-forging roughening, microwave irradiation and secondary micro-forging can significantly improve the material hardness and fatigue life. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a process flow chart of the present invention;

[0027] Figure 2Schematic diagram of the size of fatigue test samples according to an embodiment of the present invention. DETAILED DESCRIPTION

[0028] The present invention will be further described below in conjunction with the accompanying drawings:

[0029] The Vickers hardness of M390 steel is usually between 700 and 750 HV, which makes it one of the hardest stainless steels on the market. Even under extreme conditions, M390 steel can maintain its high hardness and wear resistance, so it is one of the preferred materials for high-end folding knives, hunting knives and other precision tools. The raw material used in all embodiments of the present invention is M390 steel, and the sample size is a flat sample of 70×19×4 mm.

[0030] Example 1

[0031] See also Figure 1 As shown, the sample surface treatment method steps are:

[0032] 1) Soak the workpiece in alkaline solution for degreasing;

[0033] 2) Rinse with deionized water;

[0034] 3) Use 120-160μm white corundum particles to perform primary micro-forging on the workpiece surface;

[0035] 4) Soak the workpiece after primary micro-forging in an acid solution for 30 seconds, take it out and rinse it with deionized water, rinse it with alcohol, and dry it in an oven at 80°C;

[0036] 5) Place the workpiece in the microwave cavity, then evacuate the cavity or fill it with inert gas (helium, nitrogen, argon, etc.), turn on the power to start microwave heating, time 30s, microwave frequency 2.45GHz, power 3000w;

[0037] 6) After the microwave work is completed, the secondary micro-forging is immediately carried out, the particle size of the microparticles is 40-100 μm, the coverage rate is 100%, the micro-forging scanning speed is 20 mm / s, the particle shooting speed is 300 m / s, and the angle between the spray gun and the workpiece surface is 15°;

[0038] 7) Soak the micro-forged workpiece in an acid solution for 30 seconds, rinse with deionized water, rinse with alcohol, dry in an oven at 80°C, and package for later use.

[0039] The operation steps of Examples 2-5 and Comparative Examples 1-3 are the same as those of Example 1, except for the relevant parameters. The parameters and results of all Examples and Comparative Examples are listed in Table 1.

[0040] Table 1

[0041]

[0042] See also Figure 2 As shown in the figure, fatigue test refers to the performance index test of high-frequency tensile and compression test and fatigue performance, fracture mechanics performance and fatigue life of various parts under tension and compression alternating loads on metal parts. Fatigue life refers to the number of cycles of stress or strain required for fatigue failure of the material under cyclic loading. In the fatigue test, the loading waveform uses a sinusoidal waveform, the stress ratio R=-1, the dynamic load size is 935MPa, the test loading frequency range is 81~83Hz, and the laboratory temperature is maintained at about 25℃. The structural dimensions of the fatigue specimens are prepared in accordance with GB / T 15248-2008. In order to facilitate the statistical characterization of the material properties, the specimens are cut from homogeneous raw material blanks.

[0043] The sample in reference example 1 has only undergone a first-level micro-forging operation, without microwave and second-level micro-forging operations, and its fatigue life is only 538,468 times at the lowest under the action of 935MPa load. Reference example 2 has a second-level micro-forging operation, but no microwave irradiation, the hardness is increased by 5%, and the fatigue life is increased to 1,625,387 times. Reference example 3 sample has undergone microwave irradiation and second-level micro-forging operation, but there is no first-level micro-forging to roughen the sample surface, the microwave irradiation efficiency is low, and the micro-forging effect is not good, the hardness is increased to 8%, and the fatigue life is increased to 1,856,214 times. Embodiment 1-5 has undergone a complete operation of first-level micro-forging, microwave irradiation and second-level micro-forging, and the hardness is increased by more than 15%, and the fatigue life is at least more than six times that of reference example 1. It can be seen that only the first-level micro-forging roughening, microwave irradiation and second-level micro-forging can achieve a significant increase in material hardness and fatigue life.

[0044] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should fall within the scope of the claims of the present invention.

Claims

1. A method for treating high-hardness stainless steel surface using microwave-assisted micro-forging technology, characterized in that: The following steps are involved: ⑴ Soak the workpiece in alkaline solution to remove oil; ⑵ Wash with water; ⑶First-level micro-forging: Micro-forging with particles with a particle size of 100-200 μm to form a roughness of 5-20 μm; (4) Immerse the workpiece after primary micro-forging in an acid cleaning solution for 30 seconds to remove dust and oxides; ⑸ Rinse the workpiece with deionized water, alcohol, and dry it in an oven at 80°C; (6) Place the workpiece in a microwave cavity that is evacuated or filled with inert gas, and then irradiate it with microwaves; ⑺ Perform secondary micro-forging on the workpiece surface: Use particles with a particle size of 20 to 100 μm for micro-forging to strengthen the stainless steel surface and control the morphology, and generate micron-sized pits on the workpiece surface; ⑻ Pickle the workpiece after the secondary micro-forging treatment for 30 seconds to remove the fine dust particles; ⑼ Rinse with deionized water, rinse with alcohol, dry in an oven at 80℃, and package for later use.

2. The method for treating the surface of high-hardness stainless steel by microwave-assisted micro-forging technology according to claim 1, characterized in that: The alkaline degreasing in step (1) refers to immersing the workpiece in an alkaline degreasing solution for 5 to 10 minutes at 50 to 90° C. to remove oil stains and fingerprints on the surface of the workpiece.

3. The method for treating the surface of high-hardness stainless steel by microwave-assisted micro-forging technology according to claim 1, characterized in that: The water washing in step (2) refers to rinsing with deionized water for 10 to 30 seconds.

4. The method for treating the surface of high-hardness stainless steel by microwave-assisted micro-forging technology according to claim 1, characterized in that: The first-level micro-forging in step (3) is to micro-forge the workpiece surface with 120-160 μm white corundum particles to form a roughness of 5-20 μm on the workpiece surface to increase the surface's absorption of microwaves.

5. The method for treating high hardness stainless steel surface by microwave-assisted micro-forging technology according to claim 1, characterized in that: The acid cleaning solution in step (4) is composed of the following components by weight: 5 parts of sulfuric acid, 5 parts of hydrochloric acid, and 90 parts of water, and is used to remove oxide scale, metal powder generated by primary micro-forging, and residual particles embedded in the surface of the workpiece.

6. The method for treating high-hardness stainless steel surface by microwave-assisted micro-forging technology according to claim 1, characterized in that: The drying in step (5) refers to baking the workpiece in an oven at 80-120° C. for 2-5 minutes.

7. The method for treating high hardness stainless steel surface by microwave-assisted micro-forging technology according to claim 1, characterized in that: The microwave frequency in step (6) is 2.45 GHz, the radiation time is 30 to 60 s, and the radiation power is 1000 to 3000 W.

8. The method for treating high-hardness stainless steel surface by microwave-assisted micro-forging technology according to claim 1, characterized in that: The secondary micro-forging in step ⑺ refers to the particle size of the microparticles being between 20 and 100 μm, the coverage being 100%, the micro-forging scanning speed being 20 to 5 mm / s, the particle shooting speed being 200 to 350 m / s, and the angle between the spray gun and the workpiece surface being 15 to 90°.

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